BA Cutler

What are your experiences reducing understeer problems within SCCA B Stock rules? The key restriction is staying B Stock legal.

I haven't changed anything on my car yet... I've been acclimating myself to the car... messing around with tire pressures.

I imagine Nissan detuned the car's dynamics to please the liability lawyers... I guess it's just a case of identifying what hardware they used to get that sweet "John Deere" feel.

Has adding DOT legal rubber corrected what I'm feeling on the stock rubber?

Has adding Konis helped? Would DAs be more advantageous than SAs on a car with the Z's little quirks?

The front sway bar seems to be a bit stout... EVO has a bar that actually adjusts below the stock bar's setting... has anyone experimented with that lowest setting?

How about front end alignments? I remember Carter Thompson's post listing his alignment settings... Stock camber settings: Frt = 0.9 neg, Rear = 1.5 neg... Frt Toe = 0.25" Out, Rear Toe = 0.25" In. Other folks have recommended 0.168 Out/In.

It's getting closer to that time of year again, I can't wait to get some more quality time with my Z. Thanks in advance for your information sharing, we have a common "challenger" in BS... I think we all know which car I'm talking about...

zfastest

This may not help you too much with your time, but what I have done in the Z to reduce understeer is just drive it different. Having a couple years of racing under my belt in several different types of cars, you learn quickly to adjust your driving for the vehicle. I autocrossed my Z a while ago just for some play time and found that slow speed corners are a nightmare for this car, it pushes like crazy. Soooo. . . I just started pitching the car into the corners (shift weight out, then in quickly) and getting the rear tires to loose traction just enough to get enough rotation through a tight corner and not loose any speed. Some people call it drifting!?

But regardless, I always suggest to people to look within yourself to improve the performance of your car before getting into modifying it, especially with suspension bits and peices. You could quickly get in over your head with all that. But seriously, now that I've gotten comfortable tossing the Z around, I can't get it to go straight! Find a big empty spot somewhere and practice tossing it around, it will be a big help when it's autocross time.

fowlman01

iTrader: (1)

very good advice zfastest. you need to push a car to see what it really does and you might be able to use that "fault" to your advantage. I ran corvairs at autoX's and commpensated for the slow steering by unloading the back tires in tight turns and esses.

BA Cutler

Thanks for sharing. I probably should've mentioned I've been at this for twelve years... and am fairly proficient at SOLO II competition. Any set-up information to share?

rktjhn

I ran the crap out of mine last year, there are no shocks yet. Well, there is a set of Penskes Guy Ankeny made for 2300 bucks.
I played with tire pressures, alignment, and sway bar. I did the Stillen and have it set 30%+ setting. Biggest differance was more rubber in the front, I have 245's on the stock track rims, and 275 in the rear. Hoosier rep says 275 will fit the front, and I will go that route next time. Sway bar helped a lot in slaloms.
Align I did toe out up front and left the back neautral, toe in made it to hard for me to handle, in neautral setting the rear stays planted, for me any way. We had 3 cars in Utah, so we all experimented to see what would work.
Borla true dual and a KN replacement is a 25 HP differance, An 8 time Natl champ drove my car and could not beleive the differance between mine and his, he still had stock exhaust, now he dosen't.
I have a problem with going in too fast, then have to fight the car, so slower works better resulting in faster times, I still need to get in closer to the cones, read that 12 inches on on slalom cone is .12 of a second, roughly.
Hope that helps

zfastest

You could always try swapping your wider rears, up front, and put the front (smaller) wheels/tires on the rear of the car?!

But seriously, you sound like you know what your doing, so as a fellow racer, I would just suggest more rubber up front. I saw a dude using 245/45/17's on all four corners on his at the same autocross and he said it helped A LOT with the inherent understeer of the Z, and he was clicking off some pretty quick times. Might be worth a shot?

mpowers

iTrader: (7)

I am running with the stock 17" wheels with 245 kumho victoracers on all four corners. I was waiting for the koni sa before I did the sway bar, wich currently looking at the EVO brand for the adjustablility. I was not having a problem with the understeer till I did an autocross at Roebling Road. Turn 1 at Roebling they let you take at full speed wich for me was 90+ tapping the rev limiter for about 4-5 seconds this was the coner that made myself rethink about the understeer. Any other condition it was controlable. So I am waiting on the Koni's to see if will make any changes to the dynamics of the car. I made the mistake in the past with my 300ZX of putting to much on at one time (upper control arms, sway bar, koni sa, eibach, bushings) and had sevral disapointing autocross events until I worked the set up multiple difftrent ways. Hurry Koni! Good luck and Happy New Year!

zfastest

What the hell kind of autocross are you doing that you are going 90mph? Did you mean a track day or something? I'm not sure what roebling road is, I'm guessing a race track somewhere?

mpowers

iTrader: (7)

No not a track day, but yes a road course, our autocross twice a year is held at Roebling Road. We use the first two coners and the chicane with pylons to slow down some parts of the track. It is the fastest autocross I have ever done.

D'oh

I'm running 265/35-18 Kuhmo Ecsta V700 on all four corners for AutoX (also staying B stock). The equal size tires has balanced the car, but in slaloms it seems that the power steering can sometimes lag. I think this is due to the wide race tires, but maybe it's just a particular "feature" of my car.

I still have a tendency to "overdrive" at times, and roll over the front tires pretty good. I'm hoping that the EVO front sway bar set at a stiffer setting will keep the tires flatter and allow a better contact patch.

I also plan on getting the Koni's when they become available, but part of that mod is an attempt to reduce the freeway bounce issue. I plan on installing the Koni's and front sway at the same time (or, most likely, having someone install them for me so I don't have to get under the car).

-D'oh!

rktjhn

The sway bar made a huge differance in Slaloms, Carter Thompsons dad said they made one and it is set 80-90% stiffer, has dbl adj koni prototypes, and runs 275 all around. He is the man in BS for 350's right now

rktjhn

Tire pressure was another one that took a lot of playing around, with kumho I ran 38 fr and 33 rear and Hoosier I found 43 fr and 36-37 rear worked the best, for me. The big split seemed to help the understeer go away.
Breedlove runs huge pressure in the front, he says 50, but I saw 45+ on his gauge, and has 255-17 all around. He bought my old stang wheels and they fit just fine on the 17" models.

C Ray Z

iTrader: (2)

I added just the EVO front sway bar set on med with the stiffer bushings and I believe I reduced the push 50% just with this. I was still on stock tires so that was the only change. I compare my improvement to the fastest in B stock class. I picked up 1 full second on a 50 second course. Koni shocks comming and Kuhmo race rubber to be added for next season. Tire pressure like above also aids. Biggest improvement was just seat time and as you have that then the mods I suggested should be considered.

I also second the comment of reduced speed at turn in has a huge impact on quickness of turn-in.

BA Cutler

It sounds like folks have had some success with aftermarket front sway bars... which kind of baffles me... because it seems like that would induce more understeer... but that doesn't appear to be the case.

EVO sells the front bar independent of the rear... Stillen offers the front and rear as a kit... any strong opinions on who's bars work best?

It sounds like we need more time before we'll know how the Konis perform... has anyone tried a set of Ankeny's $2300 custom jobs?

The race rubber choice sounds 245 for the 17s... and either 275/35-18 Hoosiers or 265/35-18 Kumhos for the 18s. While talking about tires... does anyone have a handle on which brand has a hold on National level competition? Are there any new tires headed our way in 2004?

As far as the alignment question... how much toe out are you putting in?

Tire pressures sound like they should be about a six-seven pound difference front/rear... 43/37... I have 18s on my Touring model... I kept experimenting and found lower pressures to my liking... but I'm giving up traction for handling (less understeer) and that's probably not a good thing... so, y'all don't follow me over that cliff!

Thanks, I'm soaking up as much information as possible here. I found the comment about the Borla True Dual interesting... it sounds like folks who have it are satisfied...

...and I can certainly relate to the "going in too hot" habit... it's a hard one to break... I default to too much speed vs. too little speed. Running the "Ghost" on my PS2 has helped burn the error of my ways into my hard drive... helped, not cured.

Thanks again for the excellent dialog... keep it coming!

jmark

iTrader: (1)

Try this link:

Carter Thompson's Z!

https://my350z.com/forum/showthread....threadid=46715

PhoenixINX

You're exactly right.

Unless these new bars are infact "looser" than OEM a front alone won't help reduce the amount of understeer.

Two ways to remove understeer
- loosen the front end
- or tighten the rear

Since we know you can't touch the rear bar for stock class, we'll have to work on the front of the car.

At Crawford's we have added an extension to the front swaybar, thus giving the "looser" effect. Most importantly, still looking dead stock. Turn-in is FAR more responsive!

I still feel the Z has more sway than I prefer... even with the JICs... so perhaps bars are up next. For now I have little to no understeer.

mpowers

iTrader: (7)

I know kumho has came out with a dot legal slick to be released in January for autocross, and Hoosier has came out with a new compound as well. I read in either grassroots motorsports or sports car mag that the next issue they would be testing these new tires with popular old ones. I really like the new kumho V710, I belive that was the new designation for them.

mankeny

I RAN THE 275'S ON THE FRONT--DIDN'T LIKE THE WAY ABS WORKED WITH SAME DIA TIRE-FRONT AND REAR. I'VE GOT TWO NEW SETS OF SHOCKS FOR $2000.00 EA SET. SHOCKS HELP TO GET THE REAR ROTATING--Guy Ankeny

BA Cutler

Guy,

How did the ABS behave with the 275s up front? How many adjustments are on your shocks? Do you have a web site with your shocks on it? Thanks

mankeny

WITH THE 275'S UP front, it would go into ABS quicker, and not stop. I have dbl adj Penske's with 6 compression adj, 18 rebound-these are used (I did initial developement work with these on my own car. These are $2500.00. I got within .5 sec of Andy Mckee (60 sec course) after 3 mos in the car. I also have Single adj (rebound-18 adj) with the same internal valving as my doubles--these are new-2 sets @2000.00 ea. I sold one of these sets of singles, to a road racer--T2,SCCA--He loved them--Guy

350evo web site has a picture of singles.